Apparatus for the manufacture of cyanamid



AIDUCHEMINL APPARATUS FOR THE' MANUFAGTURE QF CYANAMID;

APPLICATION FILED JULY 15,1919.

Patented Dec. 21,1920;

//7 1 60 for Armand Dame/77in.

AI for/ 78y,

ARMANI) DUCHEMIN, OF PARIS, FRANCE.

APPARATUS FOR THE MANUFACTURE OF CYANAMTD.

Application filed July 15, 1919.

T 0 all whom it may concern:

Be it known that T, ARMAND DUCHEMIN, citizen of the Republic of France, and residing at Paris, France, have invented Tinprovements in Apparatus for the Manufacture of Cyanamid, of which the following is a a specification.

The manufacture of cyanamid by the processes a t present in use is effected by placing calcium carbid previously ground in an atmosphere of nitrogen and heating it by means of carbon rods through which an electric current is passed. As the carbon rods oppose a high resistance to the passage of the current through them, they are brought to incandescence and heat a portion of the carbid to a red heat, thus starting the reaction which is then maintained by the heat produced by the formation of nitrogenided lime.

This method of operation presents a number of disadvantages:

1. The nitrogen does not penetrate into the mass except in proportion 'to its absorption by the carbid; the inert gases introduced with the nitrogen, argon, neon and so forth, -as also those formed by the subsidiary reaction are imprisoned in the solidified mass, so that the reaction is, stopped before the nitration is complete, and a portion of the carbid is lost, in consequence of the fact that it is no longer in contact with the necessary nitrogen to convert it into cyanamid.

2. The reaction is slow in consequence of the difficulty which the nitrogen meets in penetrating into the solidified mass, the more so as the heat only acts upon a small portion of the carbid mass, this being the only portion which enters into reaction from the start. The reaction proceeds only very slowly from point to point of the whole charge in consequence of the bad conductivity of heat both of the ground carbid and of the cyanamid. Finally, the nitrogen and the inert gases imprisoned expand in consequence of the high temperature to which they are heated, so that at this temperature they occupy a considerably greater volume than they would occupy at the ordinary temperature, and consequently the reaction is slow and increases the mass of carbid which Specification of Letters Patent.

Serial No. 311,109.

forms the subject of the present invention, avolds the disadvantages herein'before referred to.

The present invention comprises the following characteristic features:

(a) Instead of allowing the nitrogen to penetrate the mass of ground carbid by simple diffusion, it is forced into this mass and must filter through the latter and drive out the inert gases which it incloses so that all the carbid is brought into contact with an excess of nitrogen which assists the reaction and renders it as complete as possible. (6) Instead ofoperating at atmospheric pressure or at pressure very near this latter, the operation is carried out under pressure by providing means for closing the furnace. The rapidity of the reaction is thus increased and intensified. This intensification of reactions by the pressure of gases is employed in a number of chemical industries, and it has been observed that reactions are accelerated nearly in proportion to the square of the absolute pressures and that reactions are more certain to take place, while at lower pressures they cannot be carried out completely, all other conditions remaining the same.

(.0) The furnace is provided with a thick 'lining of bricks of a basic material, for

example of magnesia having a density of about 3 with a specific heat of about 0.25,

Patented Dec, 231, 192d.

tltli hill which constitutes a suficiently good heat 1 regenerator for promoting'the reaction of a new charge with the heat produced by the preceding charge.

Heating is effected externally instead of centrally, thus increasing the surface which enters into reaction from the start and co nsequently accelerating the operation while reducing the cost of heating to promote this reaction. a

(d) The nitrogen enterlng the furnace is heated by circulating between the outer wall and the brickwork before reaching the carbid, which leads to a reduction in the losses in heat of the'furnace, protects the covering from the heat and finally assists the reaction by drawing into the interior of the furnace the heat which tends to es ca e.

2c) When. nitrating under pressure, as has been stated above, a number of furnaces can be placed in series for the current of nitrogen, so that this latter may be used more completely and only-inert gases with the minimum quantity of nitrogen are allowed to escape from the last furnace. This successive utilization of the nitrogen leads to a more efiicient circulation of the gases; by making the system of pipes short and well insulated, the internal heat of the furnaces is raised more regularly, which tends to intensify the reaction, thus rendering it more complete.

In the accompanying drawing is shown, by way of example a constructional form of the apparatus for carrying into effect the process according to this invention.

This apparatus is provided with a crucible (1 of sheet iron and is adapted to receive the carbid to be nitrated. The .crucible has a perforated sheet iron base I) which supports a layer or covering of asbestos, or also a layer of tough paper, corrugated paper or the like, which once carbonized, will support the carbid. This crucible is in'closed in brickwork c a forming a heat regenerator or accumulator, and an inner air-tight casing d around which is placed a covering of fibrous asbestos 6, serving as a heat insulator and as a distributer for the gases; the whole being placed in a casing f composed of sheet iron or of cast iron. 9 indicates a joint between the casing d and the outer casing f made by a packing of asbestos and sodium silicate; it indicates the brackets for holding the upper end of the a counterpoised lever which is pivotally mounted and serves to operate the cover Z,- n is a tap for reducing the pressure inside the furnace before lifting the cover; 0 0 are columns for supporting the furnace; 10 indicates the floor for working the furnace;

q is a tubular member for the admission of nitrogen into the furnace; 1' 1" are openings arranged between the bricks for the outflow f to of the gases; 8 indicates atubular member for the outlet of the gases; 2% is a plug for the removal of dust; to is an opening for the introduction of the blow pipe for heating the furnace at the commencement of working; at v are eyes for use in lifting.

the crucible a; m are angle pieces for centering the crucible in the furnace; y is the lining of'the extension or hood is; .2 is a lining of agglomerated and pounded refractory 'materials. The lever m above re-' ferred to is so mounted as to enable it not only to be rocked or swung in a vertical plane to raise or lower the cover I, but also to rock or swing horizontally, or substantially horizontally, to swing said cover to one side. The said lever is preferably forked at its point of attachment to the cover so as to avoid blocking the blow pipe opening a which, in such case, is disposed between the arms of the fork.

The operation of the apparatus is as follows:

The crucible a being in position is filled with very finely powdered carbid j.

The nitrogen enters the furnace through the tubular member 9, rises between the sheet iron casings cl 7 passing through the layer of. asbestos e which controls its circulation over the whole periphery, and then passes through the empty spaces provided for this purpose between the bricks of covering 3 being heated in its course, and finally reaching the top of the crucible a.

As the crucible rests with its whole weight upon its even lower surface on the asbestos joint 2', the nitrogen cannot escape between the crucible a and the brickwork c 0', so that it must filter through the carbid which fills the crucible.

The hot gases tend to rise, the top of the furnace being hotter than the bottom; but as the nitrogen circulates in descending, the temperature tends to remain uniform in the center of the furnace so that the reaction is kept uniform. The gases after having passed through the carbid, filter through the asbestos disk or the carbon disk formed by the tough paper placed on the perforated iron b, and which has been carbonized, and

pass through the orifices 1" to the tubular gas outlet 8. The tubular nitrogen inlet member q and the tubular gas outlet members are provided with valves for the purpose of disconnecting the furnace for emptying and recharging.

If it is desired to place a number of furnaces in series it is sufficient to connect the tubular members 9 and s of two consecutive furnaces by a system of pipes provided with a central disconnecting valve, and with branch pipes with valves on each side of the valves hereinbefore mentioned, one for the admission of nitrogen and the other for the outflow of inert gases.

For the purpose of regulating the pres sure of the furnace the outlets for nitrogen from the furnaces are connected together to a gas holder with a, safety valve for limiting the pressure.

The type of furnace hereinbefore described may be of any suitabledimensions and it may be of any suitable shape or proportions; the crucible may be omitted, the carbid in this case resting on a base which can be connected to one heat retaining lining. The heat regenerator may be of any suitable material such as bricks, metal and so forth. The furnace may be rigid or it may be pivotally mounted for discharging v purposes. I

All the parts forming the furnace may be of any suitable material without modifying the principle of the system of nitration,

. Leeaoae Instead of promoting the reaction either by direct heating or by the regeneration of solid bodies more or less finely pulverized and capable'of reacting one upon the other without the formation of a considerable gaseous mass.

For this purpose it is possible for example to use the reaction which is produced when mixin together an alkali metal, an alkaline eart metal or'the like (potassium, sodium, calcium, magnesium, aluminium, and so forth), with an oxid, a chlorid, an iodid, or a b, ornid of another metal (iron, zinc, copper, lead, and so forth), a reaction which permits of obtaining high temperatures.

The alumino-thermic process already employed for other uses gives one of the mixtures which is suitable for use in obtaining the desired result.

The process may be carried into effect by introducing any suitable receptacle, or a cartridge of suitable size, containing the desired mixture into or on the carbid in the crucible and starting the reaction or the combustion by any suitable means such as priming, percussion cap or electric current.

I claim:

1. A furnace for the production of calcium cyanamid, comprising, in combination, a central crucible to receive the carbid to be treated and provided with a perforated bottom; a support permeable to gases on said bottom; a fire-brick casing surrounding said crucible but spaced therefrom and forming a heat recuperator; an inner air-tight metal casing surrounding the fire-brick casing; an outer air-tight metal casing spaced from the inner metal casing and supporting the cover and bottom elements of the furnace; a filling of asbestos disposed in the space between the outer and inner metal casings; a pipe for supplying nitrogen to the lower portion of the furnace between said outer and inner metal casings; and an outlet pipe for the gas connected to the said lower portion of the apparatus.

2. A furnace for the production of calcium cyanamid comprising, in combination, a central crucible to receive the carbid to be treated and provided with a perforated bottom; a supportpermeable to gases on said bottom; a casing of refractory material surrounding said cruoible but spaced from it, and constituting a heat recuperator; an outer metal casing surrounding the entire furnace and supporting the cover and bottom ele-' ments of the furnace; a pipe for the introduction of nitrogen to the lower part of the furnace between the recuperator and the outer casing, and a pipe for the discharge of gases likewise disposed at the lower part of the furnace and communicating with the space situated below the support at the bottom of the crucible, the latter resting its whole weight upon the bottom of the furnace; means being provided for forming a tight joint between said crucible and the furnace bottom.

In testimony whereof I have signed my name to this specification in the presence of 76 two subscribing witnesses.

ARMAND DUCHEMIN. Witnesses:

JULEs FAYOLLET, Arman BORDILLON. 

